The need for air-filtration systems for improvement of indoor air quality is well recognized, and a substantial industry exists to manufacture, deliver, install, and maintain indoor air filtration systems. In spite of the maturity of this industry, however, there still remains substantial opportunity for improvement of indoor air quality. In particular, most of the air filtration technology developed to date is focused on removal of particulate materials from an air stream, using passive filters constructed from fibrous materials such as glass fibers, which are formed into woven or non-woven mat-like structures. These fibrous air filtration media inherently are ineffective at removal of particulates and/or molecular compounds that are smaller that the pore size created by the interengaged fibers. In addition, there is a natural limit to the size of the particles that can be removed by such filters, since decreasing pore size in this type of filter structure is concomitantly accompanied by an increase in the pressure drop across the filter. Further, these filtration media are inert to other major contributors to indoor air pollution, which are volatile and semi-volatile organic and inorganic compounds.
The need to remove volatile and semi-volatile compounds from air streams is also recognized in the air-filtration art. Most of the technologies used to date to remove volatile and semi-volatile compounds from an air stream rely on adsorption, as opposed to absorption, as a mechanism for trapping these compounds. Adsorption is a process whereby volatile molecules condense onto a surface of a filtration media. Because essentially only a monolayer of molecules can adsorb, it is necessary to provide very high surface areas in order to achieve significant loadings of the adsorbed compounds. In addition, as adsorption proceeds and the available surface for adsorption decreases, the rate of adsorption also decreases. Moreover, since all adsorbed molecules compete for the same surface sites, the presence of an innocuous adsorbent (such as water) can greatly reduce the capacity of the adsorbent for target volatile compounds. Despite these drawbacks, adsorption is the predominant route chosen to trap volatile organic compounds, primarily because it is considered by those skilled in the art to be the only method that has a kinetic rate great enough to be effective for removing significant levels of pollutants from an air stream.
What is needed in the art is a filter that overcomes one or more of the above-mentioned deficiencies associated with known filter media. Further, what is needed in the art is a filter that absorbed one or more materials from a fluid stream, and exhibits a desirable filtering load capacity compared to known filter media.